The invention relates to emergency braking of a tractor trailer or other automotive vehicle especially in a final panic situation prior to total loss of control. Trailor trucks are used to carry a great variety of goods on open roads. Control of the trailer while braking has always been a significant problem and continues to result in loss of life and property. The trailer is towed behind the tractor, being pivoted at the tractor at its forward end and rolling on a set of wheels at its rearward end. If traction between the trailer's wheels and the road surface is diminished or is lost, the trailer is subject to lateral skid forces. These forces can cause the trailer's wheels to slide sideways allowing the trailer to pendulum around the tractor. This is a frequent occurrence on wet or icy roads. When this occurs, there is very little that the driver can do to rectify the situation since further braking often accelerates the skid.
On long declines such as over mountain passes, frequent braking can cause brake "fading" or loss of braking power. This can result in a runaway truck. Mountain highways are often built with runaway truck stops. These consist of an additional lane on the side of the highway which is filled with sand. A truck, having lost its brakes, can pull over into this lane and coast to a stop safely because the tractor and the trailor both become bogged down in the soft sand. If a truck stopping lane is not available the only recourse open to the driver of a runaway is to try to gear-down and thus slow the truck by degrees until level ground is reached. Often it is not possible to engage the next lower gear of a truck having achieved a high rate of speed.
The patented prior art on the subject of the braking or slowing down of vehicles consists primarily of devices used in conjunction with the wheels of vehicles whereby friction is used to produce a drag force somewhere on the wheel itself. U.S. patent classification 188 2R has been searched and apparently is free of any sort of braking mechanism such as taught by the present invention. It is the applicants opinion that the present invention is new in this respect. The applicant believes that the invention is a new approach to the braking problems described above.